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Hiroshima-shi, Japan

Iwata N.,Chuden Engineering Consultants Co. | Sasaki T.,Suncoh Consultants Co. | Yoshinaka R.,Saitama University
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

The authors are analyzed two practical examples of large scale vertical excavations 20-30m in depth and two earthquake response analyses of the discontinuous rock slope and rock foundation of large building, and are presented the applicability of MultipleYield Model (MYM). MYM is a kind of finite element method constituted the mechanical properties of intact rock and discontinuity systems in rock mass, and can be analyzed the non-linearity of deformation under loading and unloading stress paths considering the confining pressures of rock joints. For analyzing, the geometrical models of rock mass were determined from site investigations and the physical parameters were determined by laboratory test and also considering scale effect. The results of MYM analysis were well corresponded to the measurement and it is confirmed that MYM is effective for static and dynamic response on jointed rock masses. © 2012 Taylor & Francis Group, London. Source

Uchida T.,Japan National Institute for Land and Infrastructure Management | Okamoto A.,Japan National Institute for Land and Infrastructure Management | Kanbara J.,Japan National Institute for Land and Infrastructure Management | Kuramoto K.,Chuden Engineering Consultants Co.
Italian Journal of Engineering Geology and Environment | Year: 2013

Soils and weathered bedrock have been known to slide simultaneously, with the resulting landslides sometimes moving rapidly and triggering debris flows. In this study, we refer to these landslides as deep-seated rapid (catastrophic) landslides (hereafter, DCLs). DCLs can result in serious damage, although the frequency of such disasters is generally low. Therefore, early warning systems and the construction of coun-termeasures for DCLs are important tools for disaster risk reduction. We analyzed the characteristics of recent storms that triggered DCLs in Japan. We found that several of these storms triggered multiple DCLs (multi-DCL events), although most triggered only a single DCL (single-DCL events). For short-term (<24 h) rainfall intensity, there was no significant difference in maximum rainfall intensities between storms that triggered single and multiple DCLs. Conversely, for long-term (48 or 72 h) rainfall amounts, storms that triggered multiple DCLs exhibited considerably higher rainfall amounts than storms that triggered no DCLs or a single DCL. In particular, more than 90% of storms that triggered multiple DCLs recorded rainfall of more than 600 mm per 48 h. Our results suggest that the 48-h or 72-h rainfall amounts were effective for assessing temporal changes in DCL susceptibility, but not the 1-h to 24-h rainfall amounts. This indicates that the occurrence of DCLs is strongly controlled by long-term rainfall amounts but less strongly by short-term rainfall intensity. © 2013 Sapienza Università Editrice. Source

Tsubota Y.,Chugoku Electric Power Co. | Iwakoke Y.,Chugoku Electric Power Co. | Yoshinaka R.,Saitama University | Yamaguchi K.,Chuden Engineering Consultants Co.
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

The behavior of rock masses during an earthquake is greatly influenced by the geometrical distribution of discontinuities within the rock mass. Therefore, it is very important to accurately investigate them for stability features such as geological structures constructed on the rock foundation, rock slope etc. The static mechanical properties of rock joints such as shear strength, shear stiffness etc. have been studied so far. However, the dynamic properties that are necessary for the seismic response analysis have not been investigated as much as the static studies. Because the test equipment for seismic properties of rock joints have not been developed so far and there are too many parameters to seismic properties (dynamic properties) such as frequency effect, cyclic effect etc. The authors have developed practical dynamic test equipment and investigated fundamental dynamic mechanical properties of rock joints under cyclic loading using mortar specimens from this research until now. In this study, we conducted dynamic tests of natural rock joints focused on "Ryoke gneiss" which had not been investigated and reported the seismic properties of natural rock joints in detail for the first time. As a result, we have confirmed that the dynamic shear strength is nearly equal to the static strength, but this result does not seem appropriate to other natural rock joints and it is necessary to consider more detailed experiments after understanding the surface condition of rock joints. The only sure thing is that the shear strength of seismic properties is greatly affected by the surface condition of rock joints (ex. roughness, hardness, and degree of weathering). In other words, it is an important factor to investigate the surface condition of rock joints beforehand if we are going to understand seismic properties of rock joints. Through this study, knowledge of seismic properties of rock joints could be obtained and it would contribute greatly to the development of rock engineering. © 2014 by Japanese Committee for Rock Mechanics. Source

Mori A.,ESI Japan Ltd. | Ishida S.,Chuden Engineering Consultants Co. | Shinji M.,Yamaguchi University
40th International Congress and Exposition on Noise Control Engineering 2011, INTER-NOISE 2011 | Year: 2011

The main method to reduce the blasting charge noise which occurs in a tunnel under construction is to install the sound insulation door in the tunnel. However, the numerical analysis technique to predict the accurate effect of the transmission loss in the sound insulation door is not established. In this study, we measured the blasting charge noise and the vibration of the sound insulation door in the tunnel with the blasting charge, and performed analysis and modified acoustic feature. In addition, we reproduced the noise reduction effect of the sound insulation door by statistical energy analysis method and confirmed that numerical simulation is possible by this procedure. Source

Iwata N.,Chuden Engineering Consultants Co. | Sasaki T.,Suncoh Consultants Co. | Yoshinaka R.,Saitama University | Kurooka K.,Chugoku Electric Power Co.
International Journal of Rock Mechanics and Mining Sciences | Year: 2012

This paper describes the validity of the multiple yield model (MYM) based on a comparison between predictions by MYM analysis and in-situ measurements of two large-scale vertical excavations, about 30. m in depth and 100. m in width, for nuclear power plants. MYM is a finite element method for modeling the mechanical properties of intact rock and joint systems in rock mass. The method can analyze the non-linearity of deformation under loading and unloading stress paths. The analysis was conducted by determining the geometrical model of rock mass from test adit and borehole observations of discontinuities in conditions such as orientation, spacing, and persistence. The physical parameters of intact rock and discontinuities were determined by laboratory tests using sample specimens, taking the scale effect into account. The deformation mode and displacement value determined by the MYM analysis both corresponded well with in-situ measurements. We have confirmed that MYM can estimate the actual behavior of discontinuous rocks with adequate accuracy for practical application. © 2012 Elsevier Ltd. Source

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